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Damon A H Teagle - One of the best experts on this subject based on the ideXlab platform.
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hydrothermal alteration of upper oceanic crust formed at a fast spreading ridge mineral chemical and isotopic evidence from odp site 801
Chemical Geology, 2003Co-Authors: Jeffrey C Alt, Damon A H TeagleAbstract:ODP Hole 801C penetrates >400 m into 170-Ma oceanic basement formed at a fast-spreading ridge. Most basalts are slightly (10-20%) recrystallized to saponite, calcite, minor Celadonite and iron oxyhydroxides, and trace pyrite. Temperatures estimated from oxygen isotope data for secondary minerals are 5-100 [deg]C, increasing downward. At the earliest stage, dark celadonitic alteration halos formed along fractures and Celadonite, and quartz and chalcedony formed in veins from low-temperature (2O; local increases in FeT, Ba, Th, and U; and local losses of Mg and Ni.Secondary carbonate veins have 87Sr/86Sr=0.706337-0.707046, and a negative correlation with [delta]18O results from seawater-basalt interaction. Carbonates could have formed at any time since the formation of Site 801 crust. Variable [delta]13C values (-11.2[permil] to 2.9[permil]) reflect the incorporation of oxidized organic carbon from intercalated sediments and changes in the [delta]13C of seawater over time.Compared to other oceanic basements, a major difference at Site 801 is the presence of two hydrothermal silica-iron deposits that formed from low-temperature hydrothermal fluids at the spreading axis. Basalts associated with these horizons are intensely altered (60-100%) to phyllosilicates, calcite, K-feldspar, and titanite; and exhibit large increases in K, Rb, Cs, Ba, H2O, and CO2, and losses of FeT, Mn, Mg, Ca, Na, and Sr. These effects may be common in crust formed at fast-spreading rates, but are not ubiquitous. A second important difference is that the abundance of brown oxidation halos along fractures at Site 801 is an order of magnitude less than at some other sites (2% vs. 20-30%). Relatively smooth basement topography (<100 m) and high sedimentation rate (8 m/Ma) probably restricted the access of oxygenated seawater. Basement lithostratigraphy and early low-temperature hydrothermal alteration and mineral precipitation in fractures at the spreading axis controlled permeability and limited later flow of oxygenated seawater to restricted depth intervals.
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hydrothermal alteration of upper oceanic crust formed at a fast spreading ridge mineral chemical and isotopic evidence from odp site 801
Chemical Geology, 2003Co-Authors: Damon A H TeagleAbstract:ODP Hole 801C penetrates >400 m into 170-Ma oceanic basement formed at a fast-spreading ridge. Most basalts are slightly (10–20%) recrystallized to saponite, calcite, minor Celadonite and iron oxyhydroxides, and trace pyrite. Temperatures estimated from oxygen isotope data for secondary minerals are 5–100 °C, increasing downward. At the earliest stage, dark celadonitic alteration halos formed along fractures and Celadonite, and quartz and chalcedony formed in veins from low-temperature (<100 °C) hydrothermal fluids. Iron oxyhydroxides subsequently formed in alteration halos along fractures where seawater circulated, and saponite and pyrite developed in the host rock and in zones of restricted seawater flow under more reducing conditions. Chemical changes include variably elevated K, Rb, Cs, and H2O; local increases in FeT, Ba, Th, and U; and local losses of Mg and Ni. Secondary carbonate veins have 87Sr/86Sr=0.706337–0.707046, and a negative correlation with δ18O results from seawater–basalt interaction. Carbonates could have formed at any time since the formation of Site 801 crust. Variable δ13C values (−11.2‰ to 2.9‰) reflect the incorporation of oxidized organic carbon from intercalated sediments and changes in the δ13C of seawater over time. Compared to other oceanic basements, a major difference at Site 801 is the presence of two hydrothermal silica–iron deposits that formed from low-temperature hydrothermal fluids at the spreading axis. Basalts associated with these horizons are intensely altered (60–100%) to phyllosilicates, calcite, K-feldspar, and titanite; and exhibit large increases in K, Rb, Cs, Ba, H2O, and CO2, and losses of FeT, Mn, Mg, Ca, Na, and Sr. These effects may be common in crust formed at fast-spreading rates, but are not ubiquitous. A second important difference is that the abundance of brown oxidation halos along fractures at Site 801 is an order of magnitude less than at some other sites (2% vs. 20–30%). Relatively smooth basement topography (<100 m) and high sedimentation rate (8 m/Ma) probably restricted the access of oxygenated seawater. Basement lithostratigraphy and early low-temperature hydrothermal alteration and mineral precipitation in fractures at the spreading axis controlled permeability and limited later flow of oxygenated seawater to restricted depth intervals.
Paola Bonazzi - One of the best experts on this subject based on the ideXlab platform.
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a multimethodic approach for the characterization of manganiCeladonite a new member of the Celadonite family from cerchiara mine eastern liguria italy
Mineralogical Magazine, 2017Co-Authors: Giovanni Orazio Lepore, Luca Bindi, F Di Benedetto, Enrico Mugnaioli, Cecilia Viti, Alberto Zanetti, Marco E Ciriotti, Paola BonazziAbstract:In the manganesiferous ores associated with the metacherts of the ophiolitic sequences at the Cerchiara mine, Eastern Liguria (Italy), a new Mn-bearing mineral belonging to the mica group has been recently found and characterized. High resolution transmission electron microscopy and electron diffraction tomography studies confirm that the mineral belongs to the mica group. Unit-cell parameters from the powder diffraction pattern are: a = 5.149(1), b = 8.915(1), c = 10.304(1) A, β = 102.03(1)°, space group C 2 or C 2/ m . On the basis of the electron paramagnetic resonance spectroscopic results, the Mn4+ content represents a very subordinate fraction of the total Mn, the remaining occurring as Mn3+. The Raman spectrum clearly indicates the presence of OH groups in the structure. Laser-ablation inductively-coupled-plasma mass-spectrometry measurements assess the presence of considerable amounts of Li. Assuming all Mn as Mn3+ and 22 negative charges, the empirical formula can be expressed as: (K0.83□0.17)(![Graphic][1] Mg0.80Li0.20![Graphic][2] )(Si3.89Al0.10)O10[(OH)1.92F0.08] with the sum of the octahedral cations indicating a ‘transitional’ character between a di- and a tri-octahedral structure. This formula corresponds ideally to the Mn3+ analogue of Celadonite, thus expanding the range of solid solution in the Celadonite family. The ideal end-member formula KMn3+MgSi4O10(OH)2 can be easily related to Celadonite by the homovalent substitution VIMn3+ → VIFe3+. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association, (IMA 2015-052). [1]: /embed/inline-graphic-1.gif [2]: /embed/inline-graphic-2.gif
Enrico Mugnaioli - One of the best experts on this subject based on the ideXlab platform.
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a multimethodic approach for the characterization of manganiCeladonite a new member of the Celadonite family from cerchiara mine eastern liguria italy
Mineralogical Magazine, 2017Co-Authors: Giovanni Orazio Lepore, Luca Bindi, F Di Benedetto, Enrico Mugnaioli, Cecilia Viti, Alberto Zanetti, Marco E Ciriotti, Paola BonazziAbstract:In the manganesiferous ores associated with the metacherts of the ophiolitic sequences at the Cerchiara mine, Eastern Liguria (Italy), a new Mn-bearing mineral belonging to the mica group has been recently found and characterized. High resolution transmission electron microscopy and electron diffraction tomography studies confirm that the mineral belongs to the mica group. Unit-cell parameters from the powder diffraction pattern are: a = 5.149(1), b = 8.915(1), c = 10.304(1) A, β = 102.03(1)°, space group C 2 or C 2/ m . On the basis of the electron paramagnetic resonance spectroscopic results, the Mn4+ content represents a very subordinate fraction of the total Mn, the remaining occurring as Mn3+. The Raman spectrum clearly indicates the presence of OH groups in the structure. Laser-ablation inductively-coupled-plasma mass-spectrometry measurements assess the presence of considerable amounts of Li. Assuming all Mn as Mn3+ and 22 negative charges, the empirical formula can be expressed as: (K0.83□0.17)(![Graphic][1] Mg0.80Li0.20![Graphic][2] )(Si3.89Al0.10)O10[(OH)1.92F0.08] with the sum of the octahedral cations indicating a ‘transitional’ character between a di- and a tri-octahedral structure. This formula corresponds ideally to the Mn3+ analogue of Celadonite, thus expanding the range of solid solution in the Celadonite family. The ideal end-member formula KMn3+MgSi4O10(OH)2 can be easily related to Celadonite by the homovalent substitution VIMn3+ → VIFe3+. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association, (IMA 2015-052). [1]: /embed/inline-graphic-1.gif [2]: /embed/inline-graphic-2.gif
Jody Spence - One of the best experts on this subject based on the ideXlab platform.
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in situ rb sr dating of Celadonite from altered upper oceanic crust using laser ablation icp ms ms
Chemical Geology, 2021Co-Authors: Christiaan T Laureijs, Laurence A Coogan, Jody SpenceAbstract:Abstract Interaction of seawater with oceanic lavas at low temperatures (10's of °C) away from mid-ocean ridges has been suggested to play a significant role in setting the major element composition of seawater. One of the abundant, void-filling, secondary minerals that forms during this process is the K-rich phyllosilicate Celadonite. Here, we apply a recently developed in-situ Rb-Sr dating method, using laser ablation tandem quadrupole inductively coupled mass spectrometry (LA-ICP-MS/MS), to determine the ages of Celadonites in upper ocean crust lavas. We present an analytical method and data reduction scheme for in-situ Rb-Sr dating using methyl-fluoride (CH3F) as a collision reaction gas. The 87Sr/86Sr ratios were quantified by standard sample bracketing using NIST SRM612. The 87Rb/86Sr ratios were calibrated using the MPI-DING standards ATHO-G, T1-G and StHs6/80-G. We analysed veins and amygdales in 32 samples recovered by seafloor drilling of Cretaceous and Cenozoic aged oceanic crust. The data shows that ~80% of Celadonite formed within the first 20 Myr after the crust accreted, with no systematic variation in the duration of Celadonite formation with crustal age, sedimentation history or depth in the crust. There is no resolvable difference in the ages of Celadonite precipitated in veins and amygdales suggesting infilling of both interconnected and more isolated pores within the same time interval. The fraction of Celadonite formed over any time interval after crustal accretion closely matches the fraction of hydrothermal heat loss suggesting that heat flow fraction provides a good proxy for chemical exchange in these systems. Overall, we conclude that alteration conditions within the first 20 Myr after crustal accretion must largely control the bulk chemical exchange between seawater and the upper oceanic crust.
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regionally variable timing and duration of Celadonite formation in the troodos lavas cyprus from rb sr age distributions
Chemical Geology, 2021Co-Authors: Christiaan T Laureijs, Laurence A Coogan, Jody SpenceAbstract:Abstract Celadonite (K[Mg2+,Fe2+][Fe3+,Al3+](Si4O10)(OH2)) is a common void-filling mineral in ocean floor and ophiolite lavas that forms during low-temperature, off-axis, hydrothermal alteration. Its occurrence provides important information about the sink of K from seawater into the upper oceanic crust. New age determinations for celadonitic samples from a ~20 km section of the lavas in the Troodos ophiolite, along with published ages, show that most Celadonite formed within the first ~20 Myrs after crust accretion. However, significant regional differences in the duration of Celadonite formation are observed. In comparison to a region of flat paleo-seafloor, in a paleo-seafloor topographic low Celadonite started forming later and continued forming for ~20 Myrs longer. The paleo-seafloor low is associated with abundant hydrothermal sediments which are interpreted to have played a key role in controlling the chemical conditions required for Celadonite precipitation. It is hypothesised that Celadonite formed for longer largely because these hydrothermal sediments acted as a source for labile Fe for a longer time than in the region where the Fe required for Celadonite formation was mainly leached from silicate phases. In the region of flat paleo-seafloor, sediment did not begin accumulating for ~20 Myrs after crustal accretion allowing prolonged oxidative alteration of the upper crust. This led to Fe released by silicate phase breakdown being incorporated in stable Fe3+ containing phases, such as Fe-oxyhydroxides, rather than being transported as aqueous Fe2+ to sites where Celadonite could form. If this model is correct, the uptake of K from seawater into the oceanic crust may be highly spatially heterogeneous and intimately linked to the subsurface redox conditions and the distribution of hydrothermal sediments.
Yosuke Kawachi - One of the best experts on this subject based on the ideXlab platform.
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solid solution in the Celadonite family the new minerals ferrosCeladonite k2fe super 2 2fe super 3 2si8o20 oh 4 and ferroaluminoCeladonite k2fe super 2 2al2si8o20 oh 4
American Mineralogist, 1997Co-Authors: Donald R Peacor, Douglas S Coombs, Yosuke KawachiAbstract:Celadonite-family mica minerals occurring in the Triassic Gavenwood Tuffs, Murihiku Supergroup, Hokonui Hills, Southland, New Zealand, have been analyzed by XRD, TEM, AEM, and EMPA. Packets a few unit cells to several hundred nanometers thick are intimately intergrown with chlorite, berthierine, and corrensite. Analyses of homogeneous packets, combined with analyses from the literature, imply complete or nearly complete solid solution between end-members of the Celadonite family defined by octahedral exchange involving MgFe (super 3+) , Fe (super 2+) Al, Fe (super 2+) Fe (super 3+) , and probably MgAl, and show that EMPA analyses are commonly contaminated by mixtures. Two new minerals of the Celadonite family are defined: ferroCeladonite, K 2 Fe (super 2+) 2 Fe (super 3+) 2 Si 8 O 20 (OH) 4 , and ferroaluminoCeladonite, K 2 Fe (super 2+) 2 Al 2 Si 8 O 20 (OH) 4 . The former occurs largely as submicrometer ( 3 . The calculated densities are 3.045 (3) and 2.928 (2) g/cm 3 for ferroCeladonite and ferroaluminoCeladonite, respectively. Celadonite mineral-aluminous clay mineral and Celadonite mineral-Ca-rich zeolite assemblages of the zeolite facies are related to illite-chlorite+ or -pumpellyite assemblages of higher grade by dehydration reactions, not necessarily under closed-system conditions.